Study of duration of gestation in 500 patients with spontaneous onset of labor

Munjal J. Pandya, Parul J. Kotdawala, Janki M. Pandya


Background: There have been variations in the length of gestation depending upon the ethnicity of the patient.

Methods: We studied 500 patients with spontaneous onset of labor for their duration of pregnancy from First day of Last Menstrual Period (FLMP).

Results: The average gestational age was 275 days, 5 days earlier than the Expected date of delivery (EDD). 70% of pregnancies ended before EDD, 4.8% on the day of EDD and 25.2% ended after EDD. 35.80% patients completed 39 weeks, 24% completed 40 weeks, 23.20% completed 38 weeks, 11% completed 37 weeks and only 6% completed 41 weeks. Average gestational age was 39.31 weeks for male baby and 39.36 weeks for female baby. Sex ratio derived was 915.7 females per 1000 males. Average birth weight was 2.705 kg.

Conclusions: The implication of this study is that the length of human gestation does vary according to geographic location. This may be due to genetic influences, weather conditions, food habits or some unknown factor. The clinical significance is the decision to consider a term pregnancy and a post-term pregnancy. A majority of the parturient women went in to spontaneous labour at 39 completed weeks, 5 days earlier than ‘Expected date of delivery’ calculated by Naegele’s formula. This possibility should be kept in mind when maturity assessments are made with a view to intervene in the labour process to minimize perinatal complications.


Expected date of delivery, Ethnic variation, Gestational age, Preterm

Full Text:



Cunningham FG, MacDonald PC, Gant NF. Williams obstetrics. 18th ed Norwalk, Connecticut: Appleton and Lange, 1989:258.

Gibson GB. Prolonged Pregnancy. Br Med J. 1955;2:715-9.

Patel RR, Steer P, Doyle P, Little MP, Elliott P. Does gestation vary by ethnic group? A London-based study of over 122 000 pregnancies with spontaneous onset of labour. Int J Epidemiol. 2004;33:107-13.

Savitz DA. Commentary: Ethnic differences in gestational age exist, but are they ‘normal’?. Int J Epidemiol. 2004;33:114-5.

Migone A, Emanuel I, Mueller B, Daling J, Little RE. Gestational duration and birthweight in white, black and mixed-race babies. Paediatr Perinat Epidemiol. 1991 Oct;5(4):378-91.

Mittendorf R, Williams MA, Berkey CS, Cotter PF. The length of uncomplicated human gestation. Obstet Gynecol. 1990 June;75(6):929-32.

Shiono PH, Klebanoff MA. Ethnic differences in preterm and very preterm delivery. Am J Public Health. 1986 Nov;76(11):1317-21.

Papiernik E, Alexander GR, Paneth N. Racial differences in pregnancy duration and its implications for perinatal care. Med Hypotheses. 1990 Nov;33(3):181-6.

Census of India, 2011. Available at